Datsun 240Z

Front Cross Member modifications

The front suspension on the Z car is flawed. The geometry is such that the toe will change when the suspension deflects. This is called bump steer.

One way to alleviate (though probably not eliminate) this problem is to relocate the lower pivot point, which is what I have done. In a lowered car (such as mine), this mod may also help to reduce camber losses due to suspension compression during a turn (or so I've been told - but it makes sense).

I was originally planning to do this with the cross member still bolted to the car. But there was a post on HybridZ from Mike Kelly who recommended removing the cross member. I am glad I followed this advice. The corss member was pretty easy to remove and it made the work alot easier. Of course, since it was off the car, I felt compelled to clean it, blast it and paint it, which is a whole job in and of itself.

I had read about this modification from several sources. Some said the pivot point should be moved up by a whole inch, others said 7/8 inch. Some argued for moving it out as well for increased camber and track width. In the end, I opted for 15/16 inches up (I split the difference) and 1/4 inch out. In hindsight, and after some discussion of this subject on the boards (hybridz.org), I think that I was a little hasty with this decision.
I think it still makes sense, and I don't regret having done it, but I should have been more diligent.

 

 

To do this mod, you will need a good 1/2 drill, 4 (or more) standard, 1/2 washers (whose ID is actually closer to 14.5mm) and a welder. The old washer/spacers must be removed. This involved lots and lots of grinding and pounding and chiseling.

Since I didn't feel like ordering an expensive metric drill bit (much less waiting for it to be shipped), I used a 1/2 inch drill bit. I then used a conical grinding bit in my rotary tool to widen it out to 14mm. I created a sort of a jig using a door nail whose head was about 1/2 inch diameter, welded to one of the 1/2 washers. The head of the doornail fit in the hole and the washer got clamped into position such that the nail head was pushed to the top. I tried to come up with a way to weld something else to the washer to locate the hole precisely on the xmember, but decided it would be easier to just measure and clamp.

After the holes were drilled, I widened them all out so that the pivot bolt would fit thru snugly. Then, using the inserted pivot bolt as a guide, I clamped each washer (one at a time) to the inside of the Xmember and spotted it in place. The Washer ID is a bit too large, so it's there mostly as a spacer. I thought about welding in the difference and then machining everything back flush, but realized that that would be a nightmare.

 

All images Copyright 2000, 2001, Jeremy Roth, All rights reserved.
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